Process for producing blends of syndiotactic 1,2-polybutadiene and rubbery elastomers

ABSTRACT

Blends of syndiotactic 1,2-polybutadiene and rubbery elastomers are prepared by a process that comprises polymerizing 1,3-butadiene monomer into syndiotactic 1,2-polybutadiene within a rubber cement of at least one rubbery elastomer by using a chromium-based or molybdenum-based catalyst composition.

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/548,181, filed on Apr. 13, 2000, now U.S. Pat. No. 6,291,591and Ser. No. 09/548,555 filed on Apr. 13, 2000 now U.S. Pat. No.6,303,692.

FIELD OF THE INVENTION

The present invention is directed toward a process for producing blendsof syndiotactic 1,2-polybutadiene and rubbery elastomers.

BACKGROUND OF THE INVENTION

Syndiotactic 1,2-polybutadiene is a crystalline thermoplastic resin thathas a stereoregular structure in which the side-chain vinyl groups arelocated alternately on the opposite sides in relation to the polymericmain chain. Syndiotactic 1,2-polybutadiene is a unique material thatexhibits the properties of both plastics and rubber, and therefore ithas many uses. For example, films, fibers, and various molded articlescan be made by utilizing syndiotactic 1,2-polybutadiene. It can also beblended into and co-cured with natural and synthetic rubbers.

Syndiotactic 1,2-polybutadiene can be made by solution, emulsion, orsuspension polymerization. Generally, syndiotactic 1,2-polybutadiene hasa melting temperature within the range of about 195° C. to about 215°C., but due to processability considerations, it is generally desirablefor syndiotactic 1,2-polybutadiene to have a melting temperature of lessthan about 195° C.

Because syndiotactic 1,2-polybutadiene is insoluble in common solventsat normal polymerization temperatures, a common technical difficulty inthe synthesis of syndiotactic 1,2-polybutadiene is that thepolymerization mixture is an extremely thick slurry at the commerciallydesirable polymer concentration of 10% to 25% by weight. This thickslurry becomes difficult to stir and transfer, thereby diminishing heattransfer efficiency and interfering with proper process control. Also,the slurry contributes to reactor fouling due to the undesirablebuild-up of insoluble polymer on the baffles, agitator blades, agitatorshafts, and walls of the polymerization reactor. It is thereforenecessary to clean the reactor on a regular basis, which results infrequent shutdowns of continuous processes and serious limitations ofthe run length of batch processes. The task of cleaning the fouledreactor is generally difficult and time-consuming. All of thesedrawbacks detrimentally affect productivity and the cost of operation.It would be advantageous to develop a method of synthesizingsyndiotactic 1,2-polybutadiene that avoids this frequent reactor foulingproblem.

Various transition metal catalyst systems based on cobalt, titanium,vanadium, chromium, and molybdenum for the preparation of syndiotactic1,2-polybutadiene have been reported. The majority of these catalystsystems, however, have no practical utility because they have lowcatalytic activity or poor stereoselectivity, and in some cases theyproduce low molecular weight polymers or partially crosslinked polymersunsuitable for commercial use.

The following two cobalt-based catalyst systems are well known for thepreparation of syndiotactic 1,2-polybutadiene on a commercial scale: (1)a catalyst system containing cobalt bis(acetylacetonate),triethylaluminum, water, and triphenylphosphine (U.S. Pat. Nos.3,498,963 and 4,182,813), and (2) a catalyst system containing cobalttris(acetylacetonate), triethylaluminum, and carbon disulfide (U.S. Pat.No. 3,778,424). These cobalt-based catalyst systems also have seriousdisadvantages.

The first cobalt catalyst system referenced above yields syndiotactic1,2-polybutadiene having very low crystallinity. Also, this catalystsystem develops sufficient catalytic activity only when halogenatedhydrocarbon solvents are used as the polymerization medium, andhalogenated solvents present toxicity problems.

The second cobalt catalyst system referenced above uses carbon disulfideas one of the catalyst components. Because of its low flash point,obnoxious smell, high volatility, and toxicity, carbon disulfide isdifficult and dangerous to use, and requires expensive safety measuresto prevent even minimal amounts escaping into the atmosphere.Furthermore, the syndiotactic 1,2-polybutadiene produced with thiscobalt catalyst system has a very high melting temperature of about200-210° C., which makes it difficult to process the polymer. Althoughthe melting temperature of the syndiotactic 1,2-polybutadiene producedwith this cobalt catalyst system can be reduced by employing a catalystmodifier as a fourth catalyst component, the presence of this catalystmodifier has adverse effects on the catalyst activity and polymeryields. Accordingly, many restrictions are required for the industrialutilization of these cobalt-based catalyst systems.

It is well known that the physical properties of rubbery elastomers canbe improved by blending crystalline polymers therein. For example,incorporating syndiotactic 1,2-polybutadiene into rubber compositionsthat are utilized in the supporting carcass of tires greatly improvesthe green strength of those compositions. Also, incorporatingsyndiotactic 1,2-polybutadiene into tire tread compositions can reducethe heat build-up and improve the wear characteristics of tires. Thegreen strength of synthetic rubbers such as cis-1,4-polybutadiene canalso be improved by incorporating a small amount of syndiotactic1,2-polybutadiene.

Blends of crystalline polymers and rubbery elastomers are typicallyprepared by standard mixing techniques. For example, these blends can beprepared by mixing or kneading and heat-treating a crystalline polymerand a rubbery elastomer by utilizing generally known mixing equipmentsuch as a Banbury mixer, a Brabender mixer, an extruder, a kneader, or amill mixer. These high-temperature mixing procedures, however, havecertain drawbacks including high processing costs, polymer degradationand crosslinking, inadequate mixing, as well as various processlimitations. Due to the high vinyl content of syndiotactic1,2-polybutadiene, polymer degradation and crosslinking is aparticularly severe problem for mixing syndiotactic 1,2-polybutadienewith elastomers at high temperatures.

Attempts to polymerize 1,3-butadiene into syndiotactic 1,2-polybutadienewithin a rubber cement have been hampered by the same catalystinefficiencies and toxicities mentioned above. For example, U.S. Pat.No. 4,379,889 teaches polymerizing 1,3-butadiene into syndiotactic1,2-polybutadiene within a rubber cement by using a catalyst systemcomprising a cobalt compound, a dialkylaluminum halide, carbondisulfide, and an electron donative compound. And, U.S. Pat. No.5,283,294 teaches a similar process that employs a catalyst systemcomprising a cobalt compound, an organoaluminum compound, and carbondisulfide. These methods, however, are inferior because the catalystsystems that are employed suffer from the foregoing disadvantages.

Therefore, it would be advantageous to develop a new and significantlyimproved process for producing blends of syndiotactic 1,2-polybutadieneand rubbery elastomers.

SUMMARY OF THE INVENTION

In general, the present invention provides a process for preparingblends of syndiotactic 1,2-polybutadiene and rubbery elastomerscomprising the steps of (1) providing a mixture of a rubber cement and1,3-butadiene monomer; and (2) preparing a catalyst composition, wherethe catalyst composition is prepared by combining, outside the presenceof the mixture of rubber cement and monomer, (a) a chromium-containingcompound, (b) a hydrogen phosphite, and (c) an organomagnesium compoundor (a) a molybdenum-containing compound, (b) a hydrogen phosphite, and(c) an organoaluminum compound, and (3) adding the catalyst compositionto the mixture and thereby polymerizing the 1,3-butadiene monomer intosyndiotactic 1,2-polybutadiene within the rubber cement.

The present invention further provides a process for preparing blends ofsyndiotactic 1,2-polybutadiene and rubbery elastomers comprising thesteps of (1) providing a mixture of high cis-1,4-polybutadiene rubbercement and 1,3-butadiene monomer, and (2) preparing a catalystcomposition, where the catalyst composition is prepared by combining,outside the presence of the mixture of rubber cement and monomer, (a) achromium-containing compound, (b) a hydrogen phosphite, and (c) anorganomagnesium compound or (a) a molybdenum-containing compound, (b) ahydrogen phosphite, and (c) an organoaluminum compound, and (3) addingthe catalyst composition to the mixture and thereby polymerizing the1,3-butadiene monomer into syndiotactic 1,2-polybutadiene within therubber cement.

Advantageously, the process of this invention directly provides blendsof syndiotactic 1,2-polybutadiene and rubbery elastomers by synthesizingsyndiotactic 1,2-polybutadiene within a rubber cement and therebyobviates the need for high-temperature mixing. Also, good dispersion ofsyndiotactic 1,2-polybutadiene throughout rubbery elastomers can beeasily and economically achieved. Significantly, the process of thisinvention eliminates the problems of high processing costs, polymerdegradation and crosslinking, inadequate mixing, and various processlimitations that are associated with high-temperature mixing procedures.The process of this invention also alleviates the problems of polymercement thickness and reactor fouling that are associated with thesynthesis of syndiotactic 1,2-polybutadiene in the absence of a rubberyelastomer.

In addition, the catalyst systems employed in this invention have veryhigh catalytic activity and stereoselectivity for the syndiospecificpolymerization of 1,3-butadiene. This activity and selectivity, amongother advantages, allows syndiotactic 1,2-polybutadiene to be producedin very high yields within a rubber cement. Additionally, these catalystcompositions do not contain carbon disulfide, and therefore thetoxicity, objectionable smell, dangers, and expense associated with theuse of carbon disulfide are eliminated. Further, the chromium ormolybdenum compounds are generally stable, inexpensive, relativelyinnocuous, and readily available. Furthermore, this catalystcompositions have high catalytic activity in a wide variety of solventsincluding the environmentally-preferred nonhalogenated solvents such asaliphatic and cycloaliphatic hydrocarbons.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is generally directed toward a process forproducing blends of syndiotactic 1,2-polybutadiene and rubberyelastomers. Blends of syndiotactic 1,2-polybutadiene and rubberyelastomers can be directly produced by polymerizing 1,3-butadienemonomer into syndiotactic 1,2-polybutadiene within a rubber cement byusing chromium-based or molybdenum-based catalyst compositions.

According to the process of the present invention, blends ofsyndiotactic 1,2-polybutadiene and rubbery elastomers are produced bythe steps of: (1) providing a mixture of a rubber cement and1,3-butadiene monomer, where the rubber cement includes at least onerubbery elastomer within an organic solvent, and (2) polymerizing the1,3-butadiene monomer into syndiotactic 1,2-polybutadiene within therubber cement by using a chromium-based or molybdenum-based catalystcomposition. The chromium-based catalyst composition is formed bycombing (a) a chromium-containing compound, (b) a hydrogen phosphite,and (c) an organomagnesium compound. The molybdenum-based catalystcomposition is formed by combining (a) a molybdenum-containing compound,(b) a hydrogen phosphite, and (c) an organoaluminum compound.

Although the preferred embodiment of the present invention is directedtoward the polymerization of 1,3-butadiene into syndiotactic1,2-polybutadiene within a rubber cement, other conjugated dienemonomers can be polymerized to form conjugated diene polymers,preferably crystalline polymers, within a rubber cement.

The rubber cement employed in this invention is a solution, preferablyviscous, of at least one rubbery elastomer in an organic solvent.Virtually any type of rubbery elastomer can be used to prepare therubber cement. Some specific examples of suitable rubbery elastomersinclude, but are not limited to, natural rubber, low-vinylpolybutadiene, cis-1,4-polybutadiene, amorphous 1,2-polybutadiene,low-vinyl polyisoprene, cis-1,4-polyisoprene, polyisobutylene, neoprene,ethylene-propylene copolymer rubber (EPR), styrene-butadiene rubber(SBR), styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber(SIBR), styrene-butadiene-styrene block copolymer (SBS),styrene-butadiene block copolymer (SB), hydrogenatedstyrene-butadiene-styrene block copolymer (SEBS), hydrogenatedstyrene-butadiene block copolymer (SEB), styrene-isoprene-styrene blockcopolymer (SIS), styrene-isoprene block copolymer (SI), hydrogenatedstyrene-isoprene-styrene block copolymer (SEPS), hydrogenatedstyrene-isoprene block copolymer (SEP), polysulfide rubber, acrylicrubber, urethane rubber, silicone rubber, epichlorohydrin rubber, andthe like. Mixtures of the above rubbery elastomers may also be used.These rubbery elastomers are well known and, for the most part, arecommercially available. Also, those skilled in the art will be able toreadily synthesize these rubbery elastomers by using techniques that arewell known in the art.

The rubber cement can be prepared by dissolving the above-mentionedrubbery elastomers in an organic solvent. When commercially availablerubbery elastomers are employed to prepare the rubber cement, it may benecessary to purify the commercial products before use in order toremove residual water and additives that may become catalyst poisons inthe subsequent step of polymerizing 1,3-butadiene monomer intosyndiotactic 1,2-polybutadiene within the rubber cement.

In a preferred embodiment, the rubber cement is prepared in situ bypolymerizing one or more appropriate monomers into rubbery elastomers inan organic solvent within the same reactor that is subsequently used forpolymerizing 1,3-butadiene into syndiotactic 1,2-polybutadiene. As notedabove, many methods of synthesizing the above-mentioned rubberyelastomers are well known in the art. Preferably, however, the catalystutilized in preparing the rubbery elastomers should not contain anyingredients that may interfere with the catalyst subsequently used inthe step of polymerizing 1,3-butadiene monomer into syndiotactic1,2-polybutadiene within the rubber cement.

Coordination catalyst systems, which are well known in the art, can beused for preparing the rubber cement of rubbery elastomers in situ. Forexample, lanthanide-based catalyst systems comprising a lanthanidecompound such as a neodymium compound, an alkylating agent, and a sourceof halogen are described in U.S. Pat. Nos. 3,297,667; 3,541,063; and3,794,604, which are incorporated herein by reference. Theselanthanide-based catalyst systems are particularly useful forpolymerizing 1,3-butadiene monomer into cis-1,4-polybutadiene rubber.When a coordination catalyst such as the lanthanide-based system is usedto synthesize rubbery elastomers, the catalyst is preferably inactivatedby adding a terminator prior to proceeding with the synthesis ofsyndiotactic 1,2-polybutadiene within the rubber cement. Suitableterminators include, but are not limited to, alcohols, carboxylic acids,inorganic acids, water, and mixtures thereof. It is not alwaysnecessary, however, to add a terminator to inactivate the catalystsystem used to synthesize the rubbery elastomers since it is believedthat the catalyst may be inactivated by the hydrogen phosphite componentof catalyst composition that is subsequently used to synthesize thesyndiotactic 1,2-polybutadiene. This has been found to be true in thecase where a coordination catalyst that includes a neodymium compound,an alkylating agent, and a source of halogen ion is used to synthesizethe rubbery elastomers.

Also, anionic polymerization initiators, which are well known in theart, can be used for preparing the rubber cement of rubbery elastomersin situ. These initiators include, but are not limited to, organolithiuminitiators such as butyllithium or functional initiators such as lithiumamide initiators, aminoalkyl lithium initiators, and organotin lithiuminitiators. Exemplary initiators are described in U.S. Pat. Nos.5,153,159; 5,268,439; 5,274,106; 5,238,893; 5,332,810; 5,329,005;5,578,542; 5,393,721; 5,491,230; 5,521,309; 5,496,940; 5,574,109;5,523,364; 5,527,753; and 5,550,203. These initiators are particularlyuseful for synthesizing conjugated diene elastomers or copolymers ofconjugated diene monomers and vinyl-substituted aromatic monomers. Whenan anionic initiator is used to prepare the rubbery elastomers, it ispreferred to quench the polymerization by adding a terminator prior toproceeding with the synthesis of syndiotactic 1,2-polybutadiene withinthe rubber cement. Suitable terminators include, but are not limited to,metal halides, organic halides, alcohols, carboxylic acids, inorganicacids, sulfonic acid, water, and mixtures thereof. Metal halides, suchas diethylaluminum chloride and ethylaluminum dichloride, are preferred,as are organic halides such as trimethylsilylchloride. Failure to quenchthe anionic polymerization may interfere with the formation ofsyndiotactic 1,2-polybutadiene.

Other methods that are useful for synthesizing rubbery elastomers areknown in the art, and the practice of this invention should not belimited to the selection of any particular elastomer, or to anyparticular method for synthesizing rubbery elastomers.

Suitable monomers that can be polymerized to form the rubbery elastomersinclude conjugated diene monomers. Vinyl-substituted aromatic monomerscan be co-polymerized with one or more conjugated diene monomers to formrubbery elastomers. Some specific examples of suitable conjugated dienemonomers that can be polymerized into rubbery elastomers include1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene,2-ethyl-1,3-butadiene, isoprene, 1,3-pentadiene,2-methyl-1,3-pentadiene, 2,3-dimethyl-1,3-pentadiene,3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 1,3-hexadiene,2,4-hexadiene, and 4,5-diethyl-1,3-octadiene. Some specific examples ofsuitable vinyl-substituted aromatic monomers that can be polymerizedinto rubbery elastomers include styrene, 4-methylstyrene,α-methylstyrene, 3,5-diethylstyrene, 4-ethylstyrene, 4-propylstyrene,3,5-diethylstyrene, 2,4,6-trimethylstyrene, 4-dodecylstyrene,2,3,4,5-tetraethylstyrene, 3-methyl-5-normal-hexylstyrene,4-phenylstyrene, 2-ethyl-4-benzylstyrene, 3,5-diphenylstyrene,1-vinylnaphthalene, 3-ethyl-1-vinylnaphthalene,6-isopropyl-1-vinylnaphthalene, 6-cyclohexyl-1-vinylnapthalene,7-dodecyl-2-vinylnaphthalene, and the like, and mixtures thereof.

In preparing the rubber cement, it is normally desirable to select anorganic solvent that is inert with respect to the catalyst systems thatwill be employed to synthesize the rubbery elastomers and thesyndiotactic 1,2-polybutadiene. Suitable types of organic solvents thatcan be utilized in preparing the rubber cement include, but are notlimited to, aliphatic, cycloaliphatic, and aromatic hydrocarbons. Somerepresentative examples of suitable aliphatic solvents includen-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane,isopentane, isohexanes, isoheptanes, isooctanes, 2,2-dimethylbutane,petroleum ether, kerosene, petroleum spirits, and the like. Somerepresentative examples of suitable cycloaliphatic solvents includecyclopentane, cyclohexane, methylcyclopentane, methylcyclohexane, andthe like. Some representative examples of suitable aromatic solventsinclude benzene, toluene, xylenes, ethylbenzene, diethylbenzene,mesitylene, and the like. Commercial mixtures of the above hydrocarbonsmay also be used. For environmental reasons, aliphatic andcycloaliphatic solvents are highly preferred.

The concentration of the rubbery elastomers in the rubber cement variesdepending on the types of the rubbery elastomers and organic solventemployed. It is generally preferred that the concentration of therubbery elastomers be in a range of from about 5% to about 35% by weightof the rubber cement, more preferably from about 10% to 30% by weight ofthe rubber cement, and even more preferably from about 15% to about 25%by weight of the rubber cement.

The foregoing rubber cement is then utilized as a polymerization mediumfor the stereospecific polymerization of 1,3-butadiene monomer intosyndiotactic 1,2-polybutadiene. Thus, 1,3-butadiene monomer, catalystcomposition, and optionally additional organic solvent are added to therubber cement. The order in which the 1,3-butadiene monomer, thecatalyst composition, and the solvent are added to the rubber cementdoes not limit the scope of the invention, although it may be preferableto add the catalyst composition, or at least an ingredient thereof,prior to the addition of the 1,3-butadiene monomer.

The amount of 1,3-butadiene monomer added to the rubber cement iscontingent upon the proportion of syndiotactic 1,2-polybutadiene desiredin the resultant polymer blend. The additional organic solvent can beselected from the group of the organic solvents mentioned above for thepreparation of the rubber cement, and may be the same as or differentfrom the organic solvent used in preparing the rubber cement. Theaddition of 1,3-butadiene monomer to the rubber cement may not berequired in the case where 1,3-butadiene monomer is employed to preparethe rubbery elastomers and the polymerization is stopped before all the1,3-butadiene is consumed, thereby providing the remaining 1,3-butadienemonomer for synthesizing the syndiotactic 1,2-polybutadiene without theneed to add additional 1,3-butadiene monomer.

Chromium-based catalyst compositions useful for the polymerization of1,3-butadiene into syndiotactic 1,2-polybutadiene are described in U.S.Pat. Nos. 6,201,080 and 6,117,956, which are incorporated in theirentirety herein by reference. The preferred chromium-based catalystcomposition is formed by combining (a) a chromium-containing compound,(b) a hydrogen phosphite, and (c) an organomagnesium compound. Inaddition to the three catalyst ingredients (a), (b), and (c), otherorganometallic compounds or Lewis bases that are known in the art canalso be added, if desired.

Various chromium-containing compounds or mixtures thereof can beemployed as ingredient (a) of the chromium-based catalyst compositionutilized in this invention. It is generally advantageous to employchromium-containing compounds that are soluble in a hydrocarbon solventsuch as aromatic hydrocarbons, aliphatic hydrocarbons, or cycloaliphatichydrocarbons. Hydrocarbon-insoluble chromium-containing compounds,however, can be suspended in the polymerization medium to form thecatalytically active species and are therefore also useful.

The chromium atom in the chromium-containing compounds can be in variousoxidation states ranging from 0 up to +6. It is preferable to usedivalent chromium compounds (also called chromous compounds), whereinthe chromium is in the +2 oxidation state, and trivalent chromiumcompounds (also called chromic compounds), wherein the chromium is inthe +3 oxidation state. Suitable types of chromium-containing compoundsthat can be utilized include, but are not limited to, chromiumcarboxylates, chromium organophosphates, chromium organophosphonates,chromium organophosphinates, chromium carbamates, chromiumdithiocarbamates, chromium xanthates, chromium β-diketonates, chromiumalkoxides or aryloxides, chromium halides, chromium pseudo-halides,chromium oxyhalides, and organochromium compounds.

Some specific examples of suitable chromium carboxylates includechromium formate, chromium acetate, chromium acrylate, chromiummethacrylate, chromium valerate, chromium gluconate, chromium citrate,chromium fumarate, chromium lactate, chromium maleate, chromium oxalate,chromium 2-ethylhexanoate, chromium neodecanoate, chromium naphthenate,chromium stearate, chromium oleate, chromium benzoate, and chromiumpicolinate.

Some specific examples of suitable chromium organophosphates includechromium dibutyl phosphate, chromium dipentyl phosphate, chromiumdihexyl phosphate, chromium diheptyl phosphate, chromium dioctylphosphate, chromium bis(1-methylheptyl) phosphate, chromiumbis(2-ethylhexyl) phosphate, chromium didecyl phosphate, chromiumdidodecyl phosphate, chromium dioctadecyl phosphate, chromium dioleylphosphate, chromium diphenyl phosphate, chromium bis(p-nonylphenyl)phosphate, chromium butyl (2-ethylhexyl) phosphate, chromium(1-methylheptyl) (2-ethylhexyl) phosphate, and chromium (2-ethylhexyl)(p-nonylphenyl) phosphate.

Some specific examples of suitable chromium organophosphonates includechromium butyl phosphonate, chromium pentyl phosphonate, chromium hexylphosphonate, chromium heptyl phosphonate, chromium octyl phosphonate,chromium (1-methylheptyl) phosphonate, chromium (2-ethylhexyl)phosphonate, chromium decyl phosphonate, chromium dodecyl phosphonate,chromium octadecyl phosphonate, chromium oleyl phosphonate, chromiumphenyl phosphonate, chromium (p-nonylphenyl) phosphonate, chromium butylbutylphosphonate, chromium pentyl pentylphosphonate, chromium hexylhexylphosphonate, chromium heptyl heptylphosphonate, chromium octyloctylphosphonate, chromium (1-methylheptyl) (1-methylheptyl)phosphonate,chromium (2-ethylhexyl) (2-ethylhexyl)phosphonate, chromium decyldecylphosphonate, chromium dodecyl dodecylphosphonate, chromiumoctadecyl octadecylphosphonate, chromium oleyl oleylphosphonate,chromium phenyl phenylphosphonate, chromium (p-nonylphenyl)(p-nonylphenyl)phosphonate, chromium butyl (2-ethylhexyl)phosphonate,chromium (2-ethylhexyl) butylphosphonate, chromium (1-methylheptyl)(2-ethylhexyl)phosphonate, chromium (2-ethylhexyl)(1-methylheptyl)phosphonate, chromium (2-ethylhexyl)(p-nonylphenyl)phosphonate, and chromium (p-nonylphenyl)(2-ethylhexyl)phosphonate.

Some specific examples of suitable chromium organophosphinates includechromium butylphosphinate, chromium pentylphosphinate, chromiumhexylphosphinate, chromium heptylphosphinate, chromium octylphosphinate,chromium (1-methylheptyl)phosphinate, chromium(2-ethylhexyl)phosphinate, chromium decylphosphinate, chromiumdodecylphosphinate, chromium octadecylphosphinate, chromiumoleylphosphinate, chromium phenylphosphinate, chromium(p-nonylphenyl)phosphinate, chromium dibutylphosphinate, chromiumdipentylphosphinate, chromium dihexylphosphinate, chromiumdiheptylphosphinate, chromium dioctylphosphinate, chromiumbis(1-methylheptyl)phosphinate, chromium bis(2-ethylhexyl)phosphinate,chromium didecylphosphinate, chromium didodecylphosphinate, chromiumdioctadecylphosphinate, chromium dioleylphosphinate, chromiumdiphenylphosphinate, chromium bis(p-nonylphenyl)phosphinate, chromiumbutyl(2-ethylhexyl)phosphinate, chromium(1-methylheptyl)(2-ethylhexyl)phosphinate, and chromium(2-ethylhexyl)(p-nonylphenyl)phosphinate.

Some specific examples of suitable chromium carbamates include chromiumdimethylcarbamate, chromium diethylcarbamate, chromiumdiisopropylcarbamate, chromium dibutylcarbamate, and chromiumdibenzylcarbamate.

Some specific examples of suitable chromium dithiocarbamates includechromium dimethyldithiocarbamate, chromium diethyldithiocarbamate,chromium diisopropyldithiocarbamate, chromium dibutyldithiocarbamate,and chromium dibenzyldithiocarbamate.

Some specific examples of suitable chromium xanthates include chromiummethylxanthate, chromium ethylxanthate, chromium isopropylxanthate,chromium butylxanthate, and chromium benzylxanthate.

Some specific examples of suitable chromium -diketonates includechromium acetylacetonate, chromium trifluoroacetylacetonate, chromiumhexafluoroacetylacetonate, chromium benzoylacetonate, chromium2,2,6,6-tetramethyl-3,5-heptanedionate, chromium dioxidebis(acetylacetonate), chromium dioxide bis(trifluoroacetylacetonate),chromium dioxide bis(hexafluoroacetylacetonate), chromium dioxidebis(benzoylacetonate), and chromium dioxidebis(2,2,6,6-tetramethyl-3,5-heptanedionate).

Some specific examples of suitable chromium alkoxides or aryloxidesinclude chromium methoxide, chromium ethoxide, chromium isopropoxide,chromium 2-ethylhexoxide, chromium phenoxide, chromium nonylphenoxide,and chromium naphthoxide.

Some specific examples of suitable chromium halides include chromiumhexafluoride, chromium pentafluoride, chromium tetrafluoride, chromiumtrifluoride, chromium pentachloride, chromium tetrachloride, chromiumtrichloride, chromium tetrabromide, chromium tribromide, chromiumtriiodide, and chromium diiodide.

Some specific examples of suitable chromium pseudo-halides includechromium cyanide, chromium cyanate, chromium thiocyanate, and chromiumazide.

Some specific examples of suitable chromium oxyhalides include chromiumoxytetrafluoride, chromium dioxydifluoride, chromium oxytetrachloride,chromium oxytrichloride, chromium dioxydichloride, chromiumoxytribromide, and chromium dioxydibromide.

The term “organochromium compound” refers to any chromium compoundcontaining at least one chromium-carbon bond. Some specific examples ofsuitable organochromium compounds include tris(allyl)chromium,tris(methallyl)chromium, tris(crotyl)chromium,bis(cyclopentadienyl)chromium (also called chromocene),bis(pentamethylcyclopentadienyl)chromium, bis(ethylbenzene)chromium(also called decamethylchromocene), bis(benzene)chromium,bis(ethylbenzene)chromium, bis(mesitylene)chromium,bis(pentadienyl)chromium, bis(2,4-dimethylpentadienyl)chromium,bis(allyl)tricarbonylchromium, (cyclopentadienyl)(pentadienyl)chromium,tetra(1-norbornyl)chromium (trimethylenemethane)tetracarbonylchromium,bis(butadiene)dicarbonylchromium, (butadiene)tetracarbonylchromium, andbis (cyclooctatetraene)chromium.

Useful hydrogen phosphite compounds that can be employed as ingredient(b) of the chromium-based catalyst composition utilized in thisinvention are either acyclic hydrogen phosphites, cyclic hydrogenphosphites, or mixtures thereof.

In general, acyclic hydrogen phosphites may be represented by thefollowing keto-enol tautomeric structures:

where R¹ and R², which may be the same or different, are mono-valentorganic groups. Preferably, R¹ and R² are hydrocarbyl groups such as,but not limited to, alkyl, cycloalkyl, substituted cycloalkyl, alkenyl,cycloalkenyl, substituted cycloalkenyl, aryl, allyl, substituted aryl,aralkyl, alkaryl, and alkynyl groups, with each group preferablycontaining from 1 carbon atom, or the appropriate minimum number ofcarbon atoms to form the group, up to 20 carbon atoms. These hydrocarbylgroups may contain heteroatoms such as, but not limited to, nitrogen,oxygen, silicon, sulfur, and phosphorus atoms. The acyclic hydrogenphosphites exist mainly as the keto tautomer (shown on the left), withthe enol tautomer (shown on the right) being the minor species. Theequilibrium constant for the above-mentioned tautomeric equilibrium isdependent upon factors such as the temperature, the types of R¹ and R²groups, the type of solvent, and the like. Both tautomers may beassociated in dimeric, trimeric or oligomeric forms by hydrogen bonding.Either of the two tautomers or mixtures thereof can be employed as theingredient (b) of the chromium-based catalyst composition utilized inthis invention.

Some representative and non-limiting examples of suitable acyclichydrogen phosphites are dimethyl hydrogen phosphite, diethyl hydrogenphosphite, dibutyl hydrogen phosphite, dihexyl hydrogen phosphite,dioctyl hydrogen phosphite, didecyl hydrogen phosphite, didodecylhydrogen phosphite, dioctadecyl hydrogen phosphite,bis(2,2,2-trifluoroethyl) hydrogen phosphite, diisopropyl hydrogenphosphite, bis(3,3-dimethyl-2-butyl) hydrogen phosphite,bis(2,4-dimethyl-3-pentyl) hydrogen phosphite, di-t-butyl hydrogenphosphite, bis(2-ethylhexyl) hydrogen phosphite, dineopentyl hydrogenphosphite, bis(cyclopropylmethyl) hydrogen phosphite,bis(cyclobutylmethyl) hydrogen phosphite, bis(cyclopentylmethyl)hydrogen phosphite, bis(cyclohexylmethyl) hydrogen phosphite,dicyclobutyl hydrogen phosphite, dicyclopentyl hydrogen phosphite,dicyclohexyl hydrogen phosphite, dimethyl hydrogen phosphite, diphenylhydrogen phosphite, dinaphthyl hydrogen phosphite, dibenzyl hydrogenphosphite, bis(1-naphthylmethyl) hydrogen phosphite, diallyl hydrogenphosphite, dimethallyl hydrogen phosphite, dicrotyl hydrogen phosphite,ethyl butyl hydrogen phosphite, methyl hexyl hydrogen phosphite, methylneopentyl hydrogen phosphate, methyl phenyl hydrogen phosphate, methylcyclohexyl hydrogen phosphite, methyl benzyl hydrogen phosphite, and thelike. Mixtures of the above dihydrocarbyl hydrogen phosphites may alsobe utilized.

In general, cyclic hydrogen phosphites contain a divalent organic groupthat bridges between the two oxygen atoms that are singly-bonded to thephosphorus atoms. These cyclic hydrogen phosphites may be represented bythe following keto-enol tautomeric structures:

where R³ is a divalent organic group. Preferably, R³ is a hydrocarbylenegroup such as, but not limited to, alkylene, cycloalkylene, substitutedalkylene, substituted cycloalkylene, alkenylene, cycloalkenylene,substituted alkenylene, substituted cycloalkenylene, arylene, andsubstituted arylene groups, with each group preferably containing from 1carbon atom, or the appropriate minimum number of carbon atoms to formthe group, up to 20 carbon atoms. These hydrocarbylene groups maycontain heteroatoms such as, but not limited to, nitrogen, oxygen,silicon, sulfur, and phosphorus atoms. The cyclic hydrogen phosphitesexist mainly as the keto tautomer (shown on the left), with the enoltautomer (shown on the right) being the minor species. The equilibriumconstant for the above-mentioned tautomeric equilibrium is dependentupon factors such as the temperature, the types of R³ group, the type ofsolvent, and the like. Both tautomers may be associated in dimeric,trimeric or oligomeric forms by hydrogen bonding. Either of the twotautomers or mixtures thereof can be employed as the ingredient (b) ofthe chromium-based catalyst composition utilized in this invention.

The cyclic hydrogen phosphites may be synthesized by thetransesterification reaction of an acyclic dihydrocarbyl hydrogenphosphite (usually dimethyl hydrogen phosphite or diethyl hydrogenphosphite) with an alkylene diol or an arylene diol. Procedures for thistransesterification reaction are well known to those skilled in the art.Typically, the transesterification reaction is carried out by heating amixture of an acyclic dihydrocarbyl hydrogen phosphite and an alkylenediol or an arylene diol. Subsequent distillation of the side-productalcohol (usually methanol or ethanol) that results from thetransesterification reaction leaves the new-made cyclic hydrogenphosphite.

Some specific examples of suitable cyclic alkylene hydrogen phosphitesare 2-oxo-(2H)-5-butyl-5-ethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-5,5-dimethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-1,3,2-dioxaphosphorinane,2-oxo-(2H)-4-methyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-5-ethyl-5-methyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-5,5-diethyl-1,3,2-dioxaphosphorinane,2-oxo(2H)-5-methyl-5-propyl-1,3,2-dioxaphosphorinane2-oxo-(2H)-4-isopropyl-5,5-dimethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-4,6-dimethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-4-propyl-5-ethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-4-methyl-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-dimethyl-1,3,2-dioxaphospholane,2-oxo-(2H)-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane, and the like.Mixtures of the above cyclic alkylene hydrogen phosphites may also beutilized.

Some specific examples of suitable cyclic arylene hydrogen phosphitesare 2-oxo-(2H)-4,5-benzo-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-(3′-methylbenzo)-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-(4′-methylbenzo)-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-(4′-tert-butylbenzo)-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-naphthalo-1,3,2-dioxaphospholane, and the like. Mixturesof the above cyclic arylene hydrogen phosphites may also be utilized.

The chromium-based catalyst composition utilized in this inventionfurther comprises an organomagnesium compound, which has been designatedas ingredient (c). As used herein, the term “organomagnesium compound”refers to any magnesium compound containing at least onemagnesium-carbon bond. It is generally advantageous to employorganomagnesium compounds that are soluble in a hydrocarbon solvent.

A preferred class of organomagnesium compounds that can be utilized asingredient (c) of the chromium-based catalyst composition utilized inthis invention is represented by the general formula MgR⁴ ₂, where eachR⁴, which may be the same or different, is a mono-valent organic group,with the proviso that the group is attached to the magnesium atom via acarbon atom. Preferably, each R⁴ is a hydrocarbyl group such as, but notlimited to, alkyl, cycloalkyl, substituted cycloalkyl, alkenyl,cycloalkenyl, substituted cycloalkenyl, aryl, allyl, substituted aryl,aralkyl, alkaryl, and alkynyl groups, with each group preferablycontaining from 1 carbon atom, or the appropriate minimum number ofcarbon atoms to form the group, up to about 20 carbon atoms. Thesehydrocarbyl groups may contain heteroatoms such as, but not limited to,nitrogen, oxygen, silicon, sulfur, and phosphorus atom.

Some specific examples of suitable dihydrocarbylmagnesium compounds thatcan be utilized include diethylmagnesium, di-n-propylmagnesium,diisopropylmagnesium, dibutylmagnesium, dihexylmagnesium,diphenylmagnesium, dibenzylmagnesium, and mixtures thereof.Dibutylmagnesium is particularly useful due to its availability and itssolubility in aliphatic and cycloaliphatic hydrocarbon solvents.

Another class of organomagnesium compounds that can be utilized asingredient (c) of the catalyst composition utilized in this invention isrepresented by the general formula R⁵MgX, where R⁵ is a mono-valentorganic group, with the proviso that the group is attached to themagnesium atom via a carbon atom, and X is a hydrogen atom, a halogenatom, a carboxylate group, an alkoxide group, or an aryloxide group.Preferably, R⁵ is a hydrocarbyl group such as, but not limited to,alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl,substituted cycloalkenyl, aryl, allyl, substituted aryl, aralkyl,alkaryl, and alkynyl groups, with each group preferably containing from1 carbon atom, or the appropriate minimum number of carbon atoms to formthe group, up to about 20 carbon atoms. These hydrocarbyl groups maycontain heteroatoms such as, but not limited to, nitrogen, oxygen,silicon, sulfur, and phosphorus atoms. Preferably, X is a carboxylategroup, an alkoxide group, or an aryloxide group, with each grouppreferably containing 1 to 20 carbon atoms.

Some suitable types of organomagnesium compounds that are represented bythe general formula R⁵MgX include, but are not limited to,hydrocarbylmagnesium hydride, hydrocarbylmagnesium halide,hydrocarbylmagnesium carboxylate, hydrocarbylmagnesium alkoxide,hydrocarbylmagnesium aryloxide, and mixtures thereof.

Some specific examples of suitable organomagnesium compounds that arerepresented by the general formula R⁵MgX include methylmagnesiumhydride, ethylmagnesium hydride, butylmagnesium hydride, hexylmagnesiumhydride, phenylmagnesium hydride, benzylmagnesium hydride,methylmagnesium chloride, ethylmagnesium chloride, butylmagnesiumchloride, hexylmagnesium chloride, phenylmagnesium chloride,benzylmagnesium chloride, methylmagnesium bromide, ethylmagnesiumbromide, butylmagnesium bromide, hexylmagnesium bromide, phenylmagnesiumbromide, benzylmagnesium bromide, methylmagnesium hexanoate,ethylmagnesium hexanoate, butylmagnesium hexanoate, hexylmagnesiumhexanoate, phenylmagnesium hexanoate, benzylmagnesium hexanoate,methylmagnesium ethoxide, ethylmagnesium ethoxide, butylmagnesiumethoxide, hexylmagnesium ethoxide, phenylmagnesium ethoxide,benzylmagnesium ethoxide, methylmagnesium phenoxide, ethylmagnesiumphenoxide, butylmagnesium phenoxide, hexylmagnesium phenoxide,phenylmagnesium phenoxide, benzylmagnesium phenoxide, and the like, andmixtures thereof.

Molybdenum-based catalyst compositions are described in InternationalApplication No. PCT/US00/10274, which is incorporated herein byreference. The molybdenum-based catalyst composition is formed bycombining (a) a molybdenum-containing compound, (b) a hydrogenphosphite, and (c) an organoaluminum compound. In addition to the threecatalyst ingredients (a), (b), and (c), other organometallic compoundsor Lewis bases can also be added, if desired.

Various molybdenum-containing compounds or mixtures thereof can beemployed as ingredient (a) of the catalyst composition utilized in thisinvention. It is generally advantageous to employ molybdenum-containingcompounds that are soluble in hydrocarbon solvents such as aromatichydrocarbons, aliphatic hydrocarbons, or cycloaliphatic hydrocarbons.Hydrocarbon insoluble molybdenum-containing compounds, however, can besuspended in the polymerization medium to form the catalytically activespecies and are therefore also useful.

The molybdenum atom in the molybdenum-containing compounds can be invarious oxidation states ranging from 0 up to +6. Suitable types ofmolybdenum-containing compounds that can be utilized include, but arenot limited to, molybdenum carboxylates, molybdenum organophosphates,molybdenum organophosphonates, molybdenum organophosphinates, molybdenumcarbamates, molybdenum dithiocarbamates, molybdenum xanthates,molybdenum β-diketonates, molybdenum alkoxides or aryloxides, molybdenumhalides, molybdenum pseudo-halides, molybdenum oxyhalides, andorganomolybdenum compounds.

Some specific examples of suitable molybdenum carboxylates includemolybdenum formate, molybdenum acetate, molybdenum acrylate, molybdenummethacrylate, molybdenum valerate, molybdenum gluconate, molybdenumcitrate, molybdenum fumarate, molybdenum lactate, molybdenum maleate,molybdenum oxalate, molybdenum 2-ethylhexanoate, molybdenumneodecanoate, molybdenum naphthenate, molybdenum stearate, molybdenumoleate, molybdenum benzoate, and molybdenum picolinate.

Some specific examples of suitable molybdenum organophosphates includemolybdenum dibutyl phosphate, molybdenum dipentyl phosphate, molybdenumdihexyl phosphate, molybdenum diheptyl phosphate, molybdenum dioctylphosphate, molybdenum bis(1-methylheptyl) phosphate, molybdenumbis(2-ethylhexyl) phosphate, molybdenum didecyl phosphate, molybdenumdidodecyl phosphate, molybdenum dioctadecyl phosphate, molybdenumdioleyl phosphate, molybdenum diphenyl phosphate, molybdenumbis(p-nonylphenyl) phosphate, molybdenum butyl (2-ethylhexyl) phosphate,molybdenum (1-methylheptyl) (2-ethylhexyl) phosphate, and molybdenum(2-ethylhexyl) (p-nonylphenyl) phosphate.

Some specific examples of suitable molybdenum organophosphonates includemolybdenum butyl phosphonate, molybdenum pentyl phosphonate, molybdenumhexyl phosphonate, molybdenum heptyl phosphonate, molybdenum octylphosphonate, molybdenum (1-methylheptyl) phosphonate, molybdenum(2-ethylhexyl) phosphonate, molybdenum decyl phosphonate, molybdenumdodecyl phosphonate, molybdenum octadecyl phosphonate, molybdenum oleylphosphonate, molybdenum phenyl phosphonate, molybdenum (p-nonylphenyl)phosphonate, molybdenum butyl butylphosphonate, molybdenum pentylpentylphosphonate, molybdenum hexyl hexylphosphonate, molybdenum heptylheptylphosphonate, molybdenum octyl octylphosphonate, molybdenum(1-methylheptyl) (1-methylheptyl)phosphonate, molybdenum (2-ethylhexyl)(2-ethylhexyl)phosphonate, molybdenum decyl decylphosphonate, molybdenumdodecyl dodecylphosphonate, molybdenum octadecyl octadecylphosphonate,molybdenum oleyl oleylphosphonate, molybdenum phenyl phenylphosphonate,molybdenum (p-nonylphenyl) (p-nonylphenyl)phosphonate, molybdenum butyl(2-ethylhexyl)phosphonate, molybdenum (2-ethylhexyl) butylphosphonate,molybdenum (1-methylheptyl) (2-ethylhexyl)phosphonate, molybdenum(2-ethylhexyl) (1-methylheptyl)phosphonate, molybdenum (2-ethylhexyl)(p-nonylphenyl)phosphonate, and molybdenum (p-nonylphenyl)(2-ethylhexyl)phosphonate.

Some specific examples of suitable molybdenum organophosphinates includemolybdenum butylphosphinate, molybdenum pentylphosphinate, molybdenumhexylphosphinate, molybdenum heptylphosphinate, molybdenumoctylphosphinate, molybdenum (1-methylheptyl)phosphinate, molybdenum(2-ethylhexyl)phosphinate, molybdenum decylphosphinate, molybdenumdodecylphosphinate, molybdenum octadecylphosphinate, molybdenumoleylphosphinate, molybdenum phenylphosphinate, molybdenum(p-nonylphenyl)phosphinate, molybdenum dibutylphosphinate, molybdenumdipentylphosphinate, molybdenum dihexylphosphinate, molybdenumdiheptylphosphinate, molybdenum dioctylphosphinate, molybdenumbis(1-methylheptyl)phosphinate, molybdenum bis(2-ethylhexyl)phosphinate,molybdenum didecylphosphinate, molybdenum didodecylphosphinate,molybdenum dioctadecylphosphinate, molybdenum dioleylphosphinate,molybdenum diphenylphosphinate, molybdenumbis(p-nonylphenyl)phosphinate, molybdenumbutyl(2-ethylhexyl)phosphinate, molybdenum(1-methylheptyl)(2-ethylhexyl)phosphinate, and molybdenum(2-ethylhexyl)(p-nonylphenyl)phosphinate.

Some specific examples of suitable molybdenum carbamates includemolybdenum dimethylcarbamate, molybdenum diethylcarbamate, molybdenumdiisopropylcarbamate, molybdenum dibutylcarbamate, and molybdenumdibenzylcarbamate.

Some specific examples of suitable molybdenum dithiocarbamates includemolybdenum dimethyldithiocarbamate, molybdenum diethyldithiocarbamate,molybdenum diisopropyldithiocarbamate, molybdenumdibutyldithiocarbamate, and molybdenum dibenzyldithiocarbamate.

Some specific examples of suitable molybdenum xanthates includemolybdenum methylxanthate, molybdenum ethylxanthate, molybdenumisopropylxanthate, molybdenum butylxanthate, and molybdenumbenzylxanthate.

Some specific examples of suitable molybdenum β-diketonates includemolybdenum acetylacetonate, molybdenum trifiuoroacetylacetonate,molybdenum hexafluoroacetylacetonate, molybdenum benzoylacetonate,molybdenum 2,2,6,6-tetramethyl-3,5-heptanedionate, molybdenum dioxidebis(acetylacetonate), molybdenum dioxide bis(trifluoroacetylacetonate),molybdenum dioxide bis(hexafluoroacetylacetonate), molybdenum dioxidebis(benzoylacetonate), and molybdenum dioxidebis(2,2,6,6-tetramethyl-3,5-heptanedionate).

Some specific examples of suitable molybdenum alkoxides or aryloxidesinclude molybdenum methoxide, molybdenum ethoxide, molybdenumisopropoxide, molybdenum 2-ethylhexoxide, molybdenum phenoxide,molybdenum nonylphenoxide, and molybdenum naphthoxide.

Some specific examples of suitable molybdenum halides include molybdenumhexafluoride, molybdenum pentafluoride, molybdenum tetrafluoride,molybdenum trifluoride, molybdenum pentachloride, molybdenumtetrachloride, molybdenum trichloride, molybdenum tetrabromide,molybdenum tribromide, molybdenum triiodide, and molybdenum diiodide.

Some specific examples of suitable molybdenum pseudo-halides includemolybdenum cyanide, molybdenum cyanate, molybdenum thiocyanate, andmolybdenum azide.

Some specific examples of suitable molybdenum oxyhalides includemolybdenum oxytetrafluoride, molybdenum dioxydifluoride, molybdenumoxytetrachloride, molybdenum oxytrichloride, molybdenum dioxydichloride,molybdenum oxytribromide, and molybdenum dioxydibromide.

The term “organomolybdenum compound” refers to any molybdenum compoundcontaining at least one molybdenum-carbon bond. Some specific examplesof suitable organomolybdenum compounds include tris(allyl)molybdenum,tris(methallyl)molybdenum, tris(crotyl)molybdenum,bis(cyclopentadienyl)molybdenum,bis(pentamethylcyclopentadienyl)molybdenum, bis(ethylbenzene)molybdenum,bis(mesitylene)molybdenum, bis(pentadienyl)molybdenum,bis(2,4_dimethylpentadienyl)molybdenum, bis(allyl)tricarbonylmolybdenum,(cyclopentadienyl)(pentadienyl)molybdenum, tetra(1-norbornyl)molybdenum(trimethylenemethane)tetracarbonylmolybdenum,bis(butadiene)dicarbonylmolybdenum, (butadiene)tetracarbonylmolybdenum,and bis(cyclooctatetraene)molybdenum.

Useful hydrogen phosphite compounds that can be employed as ingredient(b) of the molybdenum-based catalyst composition utilized in thisinvention are either acyclic hydrogen phosphites, cyclic hydrogenphosphites, or mixtures thereof. These compounds are described above.

The molybdenum-based catalyst composition further comprises anorganoaluminum compound, which has been designated as ingredient (c). Asused herein, the term “organoaluminum compound” refers to any aluminumcompound containing at least one aluminum-carbon bond. It is generallyadvantageous to employ organoaluminum compounds that are soluble in ahydrocarbon solvent.

A preferred class of organoaluminum compounds that can be utilized isrepresented by the general formula AlR_(n)X_(3−n), where each R, whichmay be the same or different, is a mono-valent organic group that isattached to the aluminum atom via a carbon atom, where each X, which maybe the same or different, is a hydrogen atom, a halogen atom, acarboxylate group, an alkoxide group, or an aryloxide group, and where nis an integer of 1 to 3. Preferably, each R is a hydrocarbyl group suchas, but not limited to, alkyl, cycloalkyl, substituted cycloalkyl,alkenyl, cycloalkenyl, substituted cycloalkenyl, aryl, allyl,substituted aryl, aralkyl, alkaryl, and alkynyl groups, with each grouppreferably containing from 1 carbon atom, or the appropriate minimumnumber of carbon atoms to form the group, up to about 20 carbon atoms.These hydrocarbyl groups may contain heteroatoms such as, but notlimited to, nitrogen, oxygen, silicon, sulfur, and phosphorus atoms.Preferably, each X is a carboxylate group, an alkoxide group, or anaryloxide group, with each group preferably containing from 1 carbonatom, or the appropriate minimum number of carbon atoms to form thegroup, up to about 20 carbon atoms.

Thus, some suitable types of organoaluminum compounds that can beutilized include, but are not limited to, trihydrocarbylaluminum,dihydrocarbylaluminum hydride, hydrocarbylaluminum dihydride,hydrocarbylaluminum dihalide, dihydrocarbylaluminum halide,dihydrocarbylaluminum carboxylate, hydrocarbylaluminum bis(carboxylate),dihydrocarbylaluminum alkoxide, hydrocarbylaluminum dialkoxide,dihydrocarbylaluminum aryloxide, hydrocarbylaluminum diaryloxide, andthe like, and mixtures thereof. Trihydrocarbylaluminum compounds aregenerally preferred.

Some specific examples of organoaluminum compounds that can be utilizedinclude trimethylaluminum, triethylaluminum, triisobutylaluminum,tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum,tri-n-hexylaluminum, tri-n-octylaluminum, tricyclohexylaluminum,triphenylaluminum, tri-p-tolyl-aluminum, tribenzylaluminum,diethylphenylaluminum, diethyl-p-tolylaluminum, diethylbenzylaluminum,ethyldiphenylaluminum, ethyldi-p-tolylaluminum, ethyl-dibenzylaluminum,diethylaluminum hydride, di-n-propylaluminum hydride,diisopropylaluminum hydride, di-n-butylaluminum hydride,diisobutylaluminum hydride, di-n-octylaluminum hydride, diphenylaluminumhydride, di-p-tolyl-aluminum hydride, dibenzylaluminum hydride,phenylethylaluminum hydride, phenyl-n-propylaluminum hydride,phenylisopropylaluminum hydride, phenyl-n-butylaluminum hydride,phenylisobutylaluminum hydride, phenyl-n-octylaluminum hydride,p-tolylethylaluminum hydride, p-tolyl-n-propylaluminum hydride,p-tolylisopropylaluminum hydride, p-tolyl-n-butylaluminum hydride,p-tolyl-isobutylaluminum hydride, p-tolyl-n-octylaluminum hydride,benzylethylaluminum hydride, benzyl-n-propylaluminum hydride,benzylisopropylaluminum hydride, benzyl-n-butylaluminum hydride,benzylisobutylaluminum hydride, and benzyl-n-octylaluminum hydride,ethylaluminum dihydride, n-propylaluminum dihydride, isopropylaluminumdihydride, n-butylaluminum dihydride, isobutylaluminum dihydride,n-octylaluminum dihydride, dimethylaluminum chloride, diethylaluminumchloride, diisobutylaluminum chloride, dimethylaluminum bromide,diethylaluminum bromide, dimethylaluminum fluoride, diethylaluminumfluoride, methylaluminum dichloride, ethylaluminum dichloride,isobutylaluminum dichloride, methylaluminum dibromide, ethylaluminumdibromide, methylaluminum difluoride, ethylaluminum difluoride,methylaluminum sesquichloride, ethylaluminum sesquichloride,isobutylaluminum sesquichloride, dimethylaluminum hexanoate,diethylaluminum octoate, diisobutylaluminum 2-ethylhexanoate,dimethylaluminum neodecanoate, diethylaluminum stearate,diisobutylaluminum oleate, methylaluminum bis(hexanoate), ethylaluminumbis(octoate), isobutylaluminum bis(2-ethylhexanoate), methyl-aluminumbis(neodecanoate), ethylaluminum bis(stearate), isobutylaluminumbis(oleate), dimethylaluminum methoxide, diethylaluminum methoxide,diisobutylaluminum methoxide, dimethylaluminum ethoxide, diethylaluminumethoxide, diisobutylaluminum ethoxide, dimethylaluminum phenoxide,diethylaluminum phenoxide, diisobutylaluminum phenoxide, methylaluminumdimethoxide, ethylaluminum dimethoxide, isobutylaluminum dimethoxide,methylaluminum diethoxide, ethylaluminum diethoxide, isobutylaluminumdiethoxide, methylaluminum diphenoxide, ethylaluminum diphenoxide,isobutylaluminum diphenoxide, and the like, and mixtures thereof.

Another class of organoaluminum compounds that can be utilized isaluminoxanes. Aluminoxanes are well known in the art and compriseoligomeric linear aluminoxanes that can be represented by the generalformula:

and oligomeric cyclic aluminoxanes that can be represented by thegeneral formula:

where x is an integer of 1 to about 100, preferably about 10 to about50; y is an integer of 2 to about 100, preferably about 3 to about 20;and each R⁶, which may be the same or different, is a mono-valentorganic group that is attached to the aluminum atom via a carbon atom.Preferably, each R⁶ is a hydrocarbyl group such as, but not limited to,alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl,substituted cycloalkenyl, aryl, allyl, substituted aryl, aralkyl,alkaryl, and alkynyl groups, with each group preferably containing from1 carbon atoms, or the appropriate minimum number of carbon atoms toform the group, up to about 20 carbon atoms. These hydrocarbyl groupsmay contain heteroatoms such as, but not limited to, nitrogen, oxygen,silicon, sulfur, and phosphorus atoms. It should be noted that thenumber of moles of the aluminoxane as used in this application refers tothe number of moles of the aluminum atoms rather than the number ofmoles of the oligomeric aluminoxane molecules. This convention iscommonly employed in the art of catalysis utilizing aluminoxanes.according to known methods, such as (1) a method in which thetrihydrocarbylaluminum compound is dissolved in an organic solvent andthen contacted with water, (2) a method in which thetrihydrocarbylaluminum compound is reacted with water of crystallizationcontained in, for example, metal salts, or water adsorbed in inorganicor organic compounds, and (3) a method in which thetrihydrocarbylaluminum compound is added to the monomer or monomersolution that is to be oligomerized, and then water is added.

Some specific examples of aluminoxane compounds that can be utilizedinclude methylaluminoxane (MAO), modified methylaluminoxane (MMAO),ethylaluminoxane, butylaluminoxane, isobutylaluminoxane, and the like,and mixtures thereof. Isobutylaluminoxane is particularly useful on thegrounds of its availability and its solubility in aliphatic andcycloaliphatic hydrocarbon solvents. Modified methylaluminoxane can beformed by substituting about 20-80% of the methyl groups ofmethylaluminoxane with C₂ to C₁₂ hydrocarbyl groups, preferably withisobutyl groups, by using techniques known to those skilled in the art.

The catalyst compositions utilized in this invention have very highcatalytic activity for polymerizing 1,3-butadiene into syndiotactic1,2-polybutadiene over a wide range of total catalyst concentrations andcatalyst ingredient ratios. The polymers having the most desirableproperties, however, are obtained within a narrower range of totalcatalyst concentrations and catalyst ingredient ratios. Further, it isbelieved that the three catalyst ingredients (a), (b), and (c) caninteract to form an active catalyst species. Accordingly, the optimumconcentration for any one catalyst ingredient is dependent upon theconcentrations of the other catalyst ingredients.

With respect to the chromium-based catalyst composition, the molar ratioof the hydrogen phosphite to the chromium-containing compound (P/Cr) canbe varied from about 0.5:1 to about 50:1, more preferably from about 1:1to about 25:1, and even more preferably from about 2:1 to about 10:1.The molar ratio of the organomagnesium compound to thechromium-containing compound (Mg/Cr) can be varied from about 1:1 toabout 50:1, more preferably from about 2:1 to about 30:1, and even morepreferably from about 3:1 to about 20:1.

With respect to the molybdenum-based catalyst composition, the molarratio of the hydrogen phosphite to the molybdenum-containing compound(P/Mo) can be varied from about 0.5:1 to about 50:1, more preferablyfrom about 1:1 to about 25:1, and even more preferably from about 2:1 toabout 10:1. Where ingredient (c) of the catalyst composition utilized inthe present invention comprises an organoaluminum compound defined bythe formula AlR_(n)X_(3−n), the molar ratio of the organoaluminumcompound to the molybdenum-containing compound (Al/Mo) can be variedfrom about 1:1 to about 100:1, more preferably from about 3:1 to about50:1, and even more preferably from about 5:1 to about 25:1. Wheningredient (c) of the catalyst composition utilized in the presentinvention comprises an aluminoxane, the molar ratio of the aluminoxaneto the molybdenum-containing compound (Al/Mo) can be varied from about5:1 to about 500:1, more preferably from about 10:1 to about 200:1, andeven more preferably from about 20:1 to about 100:1.

As discussed above, the catalyst composition utilized in the presentinvention is preferably formed by combining the three catalystingredients (a), (b), and (c). Although an active catalyst species isbelieved to result from this combination, the degree of interaction orreaction between the various ingredients or components is not known withany great degree of certainty. Therefore, it should be understood thatthe term “catalyst composition” has been employed to encompass a simplemixture of the ingredients, a complex of the various ingredients that iscaused by physical or chemical forces of attraction, a chemical reactionproduct of the ingredients, or a combination of the foregoing.

The catalyst composition utilized to prepare the syndiotactic1,2-polybutadiene can be formed by combining or mixing the catalystingredients or components by using, for example, one of the followingmethods:

First, the catalyst composition may be formed in situ by adding thethree catalyst ingredients to the rubber cement containing the rubberyelastomer and 1,3-butadiene monomer in either a stepwise or simultaneousmanner. When adding the catalyst ingredients in a stepwise manner, thesequence in which the ingredients are added is not critical. With regardto the chromium-based catalyst, the organomagnesium compound ispreferably added first, followed by the chromium-containing compound,and then followed by the hydrogen phosphite. With regard to themolybdenum-based catalyst, the molybdenum-containing compound ispreferably added first, followed by the hydrogen phosphite, and thenfollowed by the organoaluminum compound.

Second, the three catalyst ingredients may be pre-mixed outside thepolymerization system at an appropriate temperature, which is generallyfrom about −20° C. to about 80° C., and the resulting catalystcomposition is then added to the rubber cement containing the rubberyelastomer and 1,3-butadiene monomer.

Third, the catalyst composition may be pre-formed in the presence ofconjugated diene monomer. That is, the three catalyst ingredients arepre-mixed in the presence of a small amount of conjugated diene monomerat an appropriate temperature, which is generally from about −20° C. toabout 80° C. The amount of 1,3-butadiene monomer that is used for thecatalyst pre-forming can range from about 1 to about 500 moles, morepreferably from about 4 to about 100 moles, and even more preferablyfrom about 10 to about 50 moles per mole of the chromium-containing ormolybdenum-containing compound. The resulting catalyst composition isthen added to the rubber cement containing the rubbery elastomer and the1,3-butadiene monomer that is to be polymerized.

Fourth, as a further variation, the catalyst composition can also beformed by using a two-stage procedure. The first stage involvescombining the chromium-containing compound and the organomagnesiumcompound or the molybdenum-containing compound and the organoaluminumcompound in the presence of a small amount of conjugated diene monomerat an appropriate temperature, which is generally from about −20° C. toabout 80° C. In the second stage, the foregoing reaction mixture and thehydrogen phosphite are charged in either a stepwise or simultaneousmanner to the rubber cement containing the rubbery elastomer and the1,3-butadiene monomer that is to be polymerized.

Fifth, an alternative two-stage procedure may also be employed. Achromium-ligand or molybdenum-ligand complex is first formed bypre-combining the chromium-containing compound or molybdenum-containingcompound and the hydrogen phosphite compound. Once formed, complex isthen combined with the organomagnesium or organoaluminum compound,respectively, to form the active catalyst species. The complex can beformed separately or in the rubber cement containing the rubberyelastomer and the 1,3-butadiene monomer that is to be polymerized. Thiscomplexation reaction can be conducted at any convenient temperature atnormal pressure, but for an increased rate of reaction, it is preferredto perform this reaction at room temperature or above. The time requiredfor the formation of the complex is usually within the range of about 10minutes to about 2 hours after mixing the chromium-containing ormolybdenum-containing compound with the hydrogen phosphite compound. Thetemperature and time used for the formation of the complex will dependupon several variables including the particular starting materials andthe solvent employed. Once formed, the complex can be used withoutisolation from the complexation reaction mixture. If desired, however,the complex may be isolated from the complexation reaction mixturebefore use.

Sixth, the three catalyst ingredients may be added to the rubber cementprior to or simultaneously with the addition of 1,3-butadiene monomer.

When a solution of the catalyst composition or one or more of thecatalyst ingredients is prepared outside the polymerization system asset forth in the foregoing methods, an organic solvent or carrier ispreferably employed. Useful solvents include hydrocarbon solvents suchas aromatic hydrocarbons, aliphatic hydrocarbons, and cycloaliphatichydrocarbons. Non-limiting examples of aromatic hydrocarbon solventsinclude benzene, toluene, xylenes, ethylbenzene, diethylbenzene,mesitylene, and the like. Non-limiting examples of aliphatic hydrocarbonsolvents include n-pentane, n-hexane, n-heptane, n-octane, n-nonane,n-decane, isopentane, isohexanes, isopentanes, isooctanes,2,2-dimethylbutane, petroleum ether, kerosene, petroleum spirits, andthe like. And, non-limiting examples of cycloaliphatic hydrocarbonsolvents include cyclopentane, cyclohexane, methylcyclopentane,methylcyclohexane, and the like. Commercial mixtures of the abovehydrocarbons may also be used. For environmental reasons, aliphatic andcycloaliphatic solvents are highly preferred. The foregoing organicsolvents may serve to dissolve the catalyst composition or ingredients,or the solvent may simply serve as a carrier in which the catalystcomposition or ingredients may be suspended.

The production of blends of syndiotactic 1,2-polybutadiene and rubberyelastomers according to this invention is accomplished by polymerizing1,3-butadiene monomer within the rubber cement by using a catalyticallyeffective amount of at least one of the foregoing catalyst compositions.To understand what is meant by a catalytically effective amount, itshould be understood that the total catalyst concentration to beemployed in the polymerization mass depends on the interplay of variousfactors such as the purity of the ingredients, the polymerizationtemperature, the polymerization rate and conversion desired, and manyother factors. Accordingly, a specific total catalyst concentrationcannot be definitively set forth except to say that catalyticallyeffective amounts of the respective catalyst ingredients should be used.Generally, the amount of the chromium-containing ormolybdenum-containing compound used can be varied from about 0.01 toabout 2 mmol per 100 g of 1,3-butadiene monomer, more preferably fromabout 0.02 to about 1.0 mmol per 100 g of 1,3-butadiene monomer, andeven more preferably from about 0.05 to about 0.5 mmol per 100 g of1,3-butadiene monomer.

In performing the polymerization of 1,3-butadiene into syndiotactic1,2-polybutadiene within the rubber cement, a molecular weight regulatormay be employed to control the molecular weight of the syndiotactic1,2-polybutadiene to be produced. As a result, the scope of thepolymerization system can be expanded in such a manner that it can beused for the production of syndiotactic 1,2-polybutadiene having a widerange of molecular weights. Suitable types of molecular weightregulators that can be utilized include, but are not limited to,α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene,1-heptene, and 1-octene; accumulated diolefins such as allene and1,2-butadiene; nonconjugated diolefins such as 1,6-octadiene,5-methyl-1,4-hexadiene, 1,5-cyclooctadiene, 3,7-dimethyl-1,6-octadiene,1,4-cyclohexadiene, 4-vinylcyclohexene, 1,4-pentadiene, 1,4-hexadiene,1,5-hexadiene, 1,6-heptadiene, 1,2-divinylcyclohexane,5-ethylidene-2-norbonene, 5-methylene-2-norbornene,5-vinyl-2-norbornene, dicyclopentadiene, and 1,2,4-trivinylcyclohexane;acetylenes such as acetylene, methylacetylene and vinylacetylene; andmixtures thereof. The amount of the molecular weight regulator used,expressed in parts per hundred parts by weight of the 1,3-butadienemonomer (phm), is from about 0.01 to about 10 phm, more preferably fromabout 0.02 to about 2 phm, and even more preferably from about 0.05 toabout 1 phm.

The molecular weight of the syndiotactic 1,2-polybutadiene to beproduced can also be effectively controlled by conducting thepolymerization of 1,3-butadiene monomer in the presence of hydrogen gas.In this case, the partial pressure of hydrogen gas is preferably fromabout 0.01 to about 50 atmospheres.

The polymerization of 1,3-butadiene into syndiotactic 1,2-polybutadienewithin the rubber cement may be carried out as a batch process, acontinuous process, or even a semi-continuous process. In thesemi-continuous process, 1,3-butadiene monomer is intermittently chargedas needed to replace that monomer already polymerized. In any case, thepolymerization is desirably conducted under anaerobic conditions byusing an inert protective gas such as nitrogen, argon or helium, withmoderate to vigorous agitation. The polymerization temperature may varywidely from a low temperature, such as −10° C. or below, to a hightemperature such as 100° C. or above, with a preferred temperature rangebeing from about 20° C. to about 90° C. The heat of polymerization maybe removed by external cooling, cooling by evaporation of the1,3-butadiene monomer or the solvent, or a combination of the twomethods. Although the polymerization pressure employed may vary widely,a preferred pressure range is from about 1 atmosphere to about 10atmospheres.

Once a desired conversion is achieved, the polymerization of1,3-butadiene monomer into syndiotactic 1,2-polybutadiene within therubber cement can be stopped by adding a polymerization terminator thatinactivates the catalyst system. Typically, the terminator employed toinactivate the catalyst system is a protic compound, which includes, butis not limited to, an alcohol, a carboxylic acid, an inorganic acid,water, or a combination thereof. An antioxidant such as2,6-di-tert-butyl-4-methylphenol may be added along with, before orafter the addition of the terminator. The amount of the antioxidantemployed is usually in the range of 0.2% to 1% by weight of the polymerproduct. When the polymerization reaction has been stopped, the blend ofsyndiotactic 1,2-polybutadiene and the rubbery elastomer can berecovered from the polymerization mixture by utilizing conventionalprocedures of desolventization and drying. For instance, the blend ofsyndiotactic 1,2-polybutadiene and the rubbery elastomer may be isolatedfrom the polymerization mixture by coagulation of the polymerizationmixture with an alcohol such as methanol, ethanol, or isopropanol, or bysteam distillation of the solvent and the unreacted 1,3-butadienemonomer, followed by filtration. The product is then dried to removeresidual amounts of solvent and water. The polymer blend produced is ahighly dispersed blend of crystalline syndiotactic 1,2-polybutadiene inthe rubbery elastomer.

Advantageously, the catalyst composition employed in this invention canbe manipulated to vary the characteristics of the syndiotactic1,2-polybutadiene in the polymer blend. Namely, the syndiotactic1,2-polybutadiene in the polymer blend made by the process of thisinvention can have various melting temperatures, molecular weights,1,2-linkage contents, and syndiotacticities, all of which are dependentupon the selection of the catalyst ingredients and the ingredientratios.

The blends of syndiotactic 1,2-polybutadiene and rubbery elastomersproduced with the process of this invention have many uses. For example,these blends can be utilized in rubber compositions that are used tomanufacture the supporting carcass, innerliner, and tread of tires. Theblends of syndiotactic 1,2-polybutadiene and rubbery elastomers are alsouseful in the manufacture of films and packaging materials and in manymolding applications.

In order to demonstrate the practice of the present invention, thefollowing examples have been prepared and tested as described in theExamples disclosed hereinbelow. The examples should not, however, beconstrued as limiting the scope of the invention. The claims will serveto define the invention.

EXAMPLES Example 1

In this experiment, a highly dispersed blend of syndiotactic1,2-polybutadiene and low-vinyl polybutadiene was prepared bypolymerizing 1,3-butadiene monomer into syndiotactic 1,2-polybutadienein the presence of a low-vinyl polybutadiene rubber cement.

The low-vinyl polybutadiene rubber cement was prepared by charging 449 gof hexanes, 911 g of a 1,3-butadiene/hexanes blend containing 22.4% byweight of 1,3-butadiene, and 0.64 mL of 1.60 M n-butyllithium in hexanesto a two-gallon stainless-steel reactor. The polymerization was carriedout at 65° C. for 6 hours. The catalyst was inactivated by the additionof 1.02 mL of 1.0 M diethylaluminum chloride. The conversion of the1,3-butadiene monomer to low-vinyl polybutadiene was determined to beessentially 100% by measuring the weight of the polymer recovered from asmall portion of the rubber cement.

After the low-vinyl polybutadiene rubber cement produced above wascooled to room temperature, 1048 g of hexanes and 2126 g of a1,3-butadiene/hexane blend containing 22.4% by weight of 1,3-butadienewere added to the rubber cement. The polymerization of the 1,3-butadienemonomer into syndiotactic 1,2-polybutadiene was initiated by theaddition of 17.5 mL of 1.0 M of dibutylmagnesium in heptane, 32.7 mL of0.0582 M chromium(III) 2-ethylhexanoate in hexanes, and 35.8 mL of 0.266M bis(2-ethylhexyl) hydrogen phosphite in hexanes. The polymerizationwas conducted at 35° C. for 4 hours. The polymerization was stopped bythe addition of 3 mL of isopropanol diluted with 50 mL of hexanes. Thepolymerization mixture was added into 10 liters of isopropanolcontaining 12 g of 2,6-di-tert-butyl-4-methylphenol. The polymer blendof syndiotactic 1,2-polybutadiene and low-vinyl polybutadiene wasisolated by filtration and dried to a constant weight under vacuum at60° C. The yield of the polymer blend was 637 g. The conversion of the1,3-butadiene monomer to the syndiotactic 1,2-polybutadiene wascalculated to be 91%. As determined by differential scanning calorimetry(DSC), the polymer blend had a glass transition temperature of −93° C.resulting from the low-vinyl polybutadiene and a melting temperature of153° C. resulting from the syndiotactic 1,2-polybutadiene.

Example 2

In this experiment, the same procedure of Example 1 was repeated exceptthat the polymerization of the 1,3-butadiene monomer into syndiotactic1,2-polybutadiene within the low-vinyl polybutadiene rubber cement wasinitiated by the addition of 21.4 mL of 1.0 M dibutylmagnesium inheptane, 40.9 mL of 0.0582 M chromium(III) 2-ethylhexanoate in hexanes,and 61.7 mL of 0.193 M of2-oxo-(2H)-5-butyl-5-ethyl-1,3,2-dioxaphosphorinane in cyclohexane.After workup of the polymerization mixture, a highly dispersed blend ofsyndiotactic 1,2-polybutadiene and low-vinyl polybutadiene was obtained.The yield of the polymer blend was 618 g. The conversion of the1,3-butadiene monomer to the syndiotactic 1,2-polybutadiene wascalculated to be 87%. As determined by differential scanning calorimetry(DSC), the polymer blend had a glass transition temperature of −93° C.resulting from the low-vinyl polybutadiene and a melting temperature of141° C. resulting from the syndiotactic 1,2-polybutadiene.

Example 3

In this experiment, a highly dispersed blend of syndiotactic1,2-polybutadiene and high cis-1,4-polybutadiene was prepared bypolymerizing 1,3-butadiene monomer into syndiotactic 1,2-polybutadienewithin a high cis-1,4-polybutadiene rubber cement.

The high cis-1,4-polybutadiene rubber cement was prepared by charging449 g of hexanes, 911 g of a 1,3-butadiene/hexanes blend containing22.4% by weight of 1,3-butadiene, 9.0 mL of 0.68 M triisobutylaluminumin hexanes, 0.41 mL of 1.0 M diethylaluminum chloride, and 0.39 mL of0.520 M neodymium(III) neodecanoate in cyclohexane to a two-gallonstainless-steel reactor. The polymerization was carried out at 80° C.for 5 hours. The conversion of the 1,3-butadiene monomer to highcis-1,4-polybutadiene was determined to be 96% by measuring the weightof the polymer recovered from a small portion of the rubber cement.

After the high cis-1,4-polybutadiene rubber cement produced above wascooled to room temperature, 1048 g of hexanes and 2126 g of a1,3-butadiene/hexanes blend containing 22.4% by weight of 1,3-butadienewere added to the rubber cement. The polymerization of the 1,3-butadienemonomer into syndiotactic 1,2-polybutadiene within the rubber cement wasinitiated by the addition of 17.1 mL of 1.0 M dibutylmagnesium inheptane, 32.7 mL of 0.0582 M chromium(III) 2-ethylhexanoate in hexanes,and 35.8 mL of 0.266 M of bis(2-ethylhexyl) hydrogen phosphite inhexanes. The polymerization was conducted at 35° C. for 4 hours. Thepolymerization was stopped by the addition of 3 mL of isopropanoldiluted with 50 mL of hexanes. The polymerization mixture was added into10 liters of isopropanol containing 12 g of2,6-di-tert-butyl-4-methylphenol. The resulting blend of syndiotactic1,2-polybutadiene and high cis-1,4-polybutadiene was isolated byfiltration and dried to a constant weight under vacuum at 60° C. Theyield of the polymer blend was 647 g. The conversion of the1,3-butadiene monomer to the syndiotactic 1,2-polybutadiene wascalculated to be 93%. As determined by differential scanning calorimetry(DSC), the polymer blend had a glass transition temperature of −103° C.and a melting temperature of −7° C. resulting from the highcis-1,4-polybutadiene, and a melting temperature of 152° C. resultingfrom the syndiotactic 1,2-polybutadiene.

Example 4

In this experiment, the same procedure of Example 3 was repeated exceptthat the polymerization of the 1,3-butadiene monomer into syndiotactic1,2-polybutadiene within the high cis-1,4-polybutadiene rubber cementwas initiated by the addition of 21.4 mL of 1.0 M dibutylmagnesium inheptane, 40.9 mL of 0.0582 M chromium(III) 2-ethylhexanoate in hexanes,and 61.7 mL of 0.193 M of2-oxo-(2H)-5-butyl-5-ethyl-1,3,2-dioxaphosphorinane in cyclohexane.After work-up of the polymerization mixture, a highly dispersed blend ofsyndiotactic 1,2-polybutadiene and high cis-1,4-polybutadiene wasobtained. The yield of the polymer blend was 632 g. The conversion ofthe 1,3-butadiene monomer to the syndiotactic 1,2-polybutadiene wascalculated to be 90%. As determined by differential scanning calorimetry(DSC), the polymer blend had a glass transition temperature of −104° C.and a melting temperature of −8° C. resulting from the highcis-1,4-polybutadiene, and a melting temperature of 140° C. resultingfrom the syndiotactic 1,2-polybutadiene.

In Examples 1-4, after the polymer blend cement was removed from thereactor, visual inspection of the interior of the reactor revealed thatthe reactor was relatively clean with minimal fouling.

Comparative Example 5

In this experiment, the polymerization of 1,3-butadiene monomer intosyndiotactic 1,2-polybutadiene was conducted in the absence of a rubbercement. In the procedure used, a two-gallon stainless-steel reactor wascharged with 2408 g of hexanes, 2126 g of a 1,3-butadiene/hexanes blendcontaining 22.4% by weight of 1,3-butadiene, 17.1 mL of 1.0 Mdibutylmagnesium in heptane, 32.7 mL of 0.0582 M chromium(III)2-ethylhexanoate in hexanes, and 35.8 mL of 0.266 M bis(2-ethylhexyl)hydrogen phosphite in hexanes. The polymerization was conducted at 35°C. for 4 hours. The polymerization was stopped by the addition of 3 mLof isopropanol diluted with 50 mL of hexanes. The polymerization mixturewas removed from the reactor and added into 10 liters of isopropanolcontaining 12 g of 2,6-di-tert-butyl-4-methylphenol, visual inspectionof the interior of the reactor revealed that severe reactor fouling hadoccurred. In particular, the blades and shafts of the agitator werecovered with large chunks of agglomerated polymer particles, and thereactor wall was coated with a thick polymer film. Due to reactorfouling, the reactor had to be opened to recover the remaining polymerinside the reactor. The total yield of the syndiotactic1,2-polybutadiene was 461 g (97%). As determined by differentialscanning calorimetry (DSC), the polymer had a melting temperature of153° C.

This comparative experiment shows that reactor fouling can be a seriousproblem in the synthesis of syndiotactic 1,2-polybutadiene in theabsence of a rubber cement. Examples 1-4 show that by utilizing theprocess of the present invention, the problem of reactor foulingassociated with the synthesis of syndiotactic 1,2-polybutadiene can begreatly reduced.

Example 6

In this experiment, a highly dispersed blend of syndiotactic1,2-polybutadiene and low-vinyl polybutadiene was prepared bypolymerizing 1,3-butadiene monomer into syndiotactic 1,2-polybutadienewithin a low-vinyl polybutadiene rubber cement.

The low-vinyl polybutadiene rubber cement was prepared by charging 449 gof hexanes, 911 g of a 1,3-butadiene/hexanes blend containing 22.4% byweight of 1,3-butadiene, and 0.64 mL of 1.60 M n-butyllithium in hexanesto a two-gallon stainless-steel reactor. The polymerization was carriedout at 65° C. for 6 hours. The catalyst was inactivated by the additionof 1.02 mL of 1.0 M diethylaluminum chloride. The conversion of the1,3-butadiene monomer to low-vinyl polybutadiene was determined to beessentially 100% by measuring the weight of the polymer recovered from asmall portion of the rubber cement.

After the low-vinyl polybutadiene rubber cement produced above wascooled to room temperature, 1048 g of hexanes and 2126 g of a1,3-butadiene/hexanes blend containing 22.4% by weight of 1,3-butadienewere added to the rubber cement. The polymerization of the 1,3-butadienemonomer into syndiotactic 1,2-polybutadiene within the rubber cement wasinitiated by the addition of 13.3 mL of 0.215 M molybdenum2-ethylhexanoate in hexanes, 43.0 mL of 0.266 M bis(2-ethylhexyl)hydrogen phosphite in hexanes, and 63.1 mL of 0.68 M oftriisobutylaluminum in hexanes. The polymerization was conducted at 65°C. for 6 hours. The polymerization was stopped by the addition of 3 mLof isopropanol diluted with 50 mL of hexanes. The polymerization mixturewas added into 10 liters of isopropanol containing 12 g of2,6-di-tert-butyl-4 methylphenol. The resulting blend of syndiotactic1,2-polybutadiene and low-vinyl polybutadiene was isolated by filtrationand dried to a constant weight under vacuum at 60° C. The yield of thepolymer blend was 632 g. The conversion of the 1,3-butadiene monomer tothe syndiotactic 1,2-polybutadiene was calculated to be 90%. Asdetermined by differential scanning calorimetry (DSC), the polymer blendhad a glass transition temperature of −93° C. resulting from thelow-vinyl polybutadiene and a melting temperature of 186° C. resultingfrom the syndiotactic 1,2-polybutadiene.

Example 7

In this experiment, the same procedure of Example 6 was repeated exceptthat the polymerization of the 1,3-butadiene monomer into syndiotactic1,2-polybutadiene within the low-vinyl polybutadiene rubber cement wasinitiated by the addition of 15.5 mL of 0.215 M molybdenum2-ethylhexanoate in hexanes, 50.1 mL of 0.266 M bis(2-ethylhexyl)hydrogen phosphite in hexanes, and 93.1 mL of 0.68 M oftri-n-butylaluminum in hexanes. After work-up of the polymerizationmixture, a highly dispersed blend of syndiotactic 1,2-polybutadiene andlow-vinyl polybutadiene was obtained. The yield of the polymer blend was618 g. The conversion of the 1,3-butadiene monomer to the syndiotactic1,2-polybutadiene was calculated to be 87%. As determined bydifferential scanning calorimetry (DSC), the polymer blend had a glasstransition temperature of −93° C. resulting from the low-vinylpolybutadiene and a melting temperature of 141° C. resulting from thesyndiotactic 1,2-polybutadiene.

Example 8

In this experiment, a highly dispersed blend of syndiotactic1,2-polybutadiene and high cis-1,4-polybutadiene was prepared bypolymerizing 1,3-butadiene monomer into syndiotactic 1,2-polybutadienewithin a high cis-1,4-polybutadiene rubber cement.

The high cis-1,4-polybutadiene rubber cement was prepared by charging449 g of hexanes, 911 g of a 1,3-butadiene/hexanes blend containing22.4% by weight of 1,3-butadiene, 9.0 mL of 0.68 M triisobutylaluminumin hexanes, 0.41 mL of 1.0 M diethylaluminum chloride, and 0.39 mL of0.520 M neodymium(III) neodecanoate in cyclohexane to a two-gallonstainless-steel reactor. The polymerization was carried out at 80° C.for 5 hours. The conversion of the 1,3-butadiene monomer to highcis-1,4-polybutadiene was determined to be 96% by measuring the weightof the polymer recovered from a small portion of the rubber cement.

After the high cis-1,4-polybutadiene rubber cement produced above wascooled to room temperature, 1048 g of hexanes and 2126 g of a1,3-butadiene/hexanes blend containing 22.4% by weight of 1,3-butadienewere added to the rubber cement. The polymerization of the 1,3-butadienemonomer into syndiotactic 1,2-polybutadiene within the rubber cement wasinitiated by the addition of 13.3 mL of 0.215 M molybdenum2-ethylhexanoate in hexanes, 43.0 mL of 0.266 M bis(2-ethylhexyl)hydrogen phosphite in hexanes, and 63.1 mL of 0.68 M oftriisobutylaluminum in hexanes. The polymerization was conducted at 65°C. for 6 hours. The polymerization was stopped by the addition of 3 mLof isopropanol diluted with 50 mL of hexanes. The polymerization mixturewas added into 10 liters of isopropanol containing 12 g of2,6-di-tert-butyl-4 methylphenol. The resulting blend of syndiotactic1,2-polybutadiene and high cis-1,4-polybutadiene was isolated byfiltration and dried to a constant weight under vacuum at 60° C. Theyield of the polymer blend was 642 g. The conversion of the1,3-butadiene monomer to the syndiotactic 1,2-polybutadiene wascalculated to be 92%. As determined by differential scanning calorimetry(DSC), the polymer blend had a glass transition temperature of −104° C.and a melting temperature of −8° C. resulting from the highcis-1,4-polybutadiene, and a melting temperature of 185° C. resultingfrom the syndiotactic 1,2-polybutadiene.

Example 9

In this experiment, the same procedure of Example 8 was repeated exceptthat the polymerization of the 1,3-butadiene monomer into syndiotactic1,2-polybutadiene within the high cis-1,4-polybutadiene rubber cementwas initiated by the addition of 15.5 mL of 0.215 M molybdenum2-ethylhexanoate in hexanes, 50.1 mL of 0.266 M bis(2-ethylhexyl)hydrogen phosphite in hexanes, and 93.1 mL of 0.68 M oftri-n-butylaluminum in hexanes. After work-up of the polymerizationmixture, a highly dispersed blend of syndiotactic 1,2-polybutadiene andhigh cis-1,4-polybutadiene was obtained. The yield of the polymer blendwas 628 g. The conversion of the 1,3-butadiene monomer to thesyndiotactic 1,2-polybutadiene was calculated to be 89%. As determinedby differential scanning calorimetry (DSC), the polymer blend had aglass transition temperature of −103° C. and a melting temperature of−7° C. resulting from the high cis-1,4-polybutadiene, and a meltingtemperature of 141° C. resulting from the syndiotactic1,2-polybutadiene.

Comparative Example 10

In this experiment, the polymerization of 1,3-butadiene monomer intosyndiotactic 1,2-polybutadiene was conducted in the absence of a rubbercement. In the procedure used, a two-gallon stainless-steel reactor wascharged with 2408 g of hexanes, 2126 g of a 1,3-butadiene/hexanes blendcontaining 22.4% by weight of 1,3-butadiene, 11.1 mL of 0.215 Mmolybdenum 2-ethylhexanoate in hexanes, 35.9 mL of 0.266 Mbis(2-ethylhexyl) hydrogen phosphite in hexanes, and 52.6 mL of 0.68 Mof triisobutylaluminum in hexanes. The polymerization was conducted at65° C. for 6 hours. The polymerization was stopped by the addition of 3mL of isopropanol diluted with 50 mL of hexanes. The polymerizationmixture was removed from the reactor and added into 10 liters ofisopropanol containing 12 g of 2,6-di-tert-butyl-4-methylphenol, visualinspection of the interior of the reactor revealed that severe reactorfouling had occurred. In particular, the blades and shafts of theagitator were covered with large chunks of agglomerated polymerparticles, and the reactor wall was coated with a thick polymer film.Due to reactor fouling, the reactor had to be opened to recover theremaining polymer inside the reactor. The total yield of thesyndiotactic 1,2-polybutadiene was 450 g (94%). As determined bydifferential scanning calorimetry (DSC), the polymer had a meltingtemperature of 189° C.

The experiment described in Comparative Example 10 shows that reactorfouling can be a serious problem in the synthesis of syndiotactic1,2-polybutadiene in the absence of a rubber cement. Examples 6-9 showthat by utilizing the process of the present invention, the problem ofreactor fouling associated with the synthesis of syndiotactic1,2-polybutadiene can be greatly reduced.

Although the present invention has been described in the above exampleswith reference to particular means, materials and embodiments, it wouldbe obvious to persons skilled in the art that various changes andmodifications may be made, which fall within the scope claimed for theinvention as set out in the appended claims. The invention is thereforenot limited to the particulars disclosed and extends to all equivalentswithin the scope of the claims.

What is claimed is:
 1. A process for preparing blends of syndiotactic1,2-polybutadiene and rubbery elastomers comprising the steps of: (1)providing a mixture of a rubber cement and 1,3-butadiene monomer; and(2) preparing a catalyst composition, where the catalyst composition isprepared by combining, outside the presence of the mixture of rubbercement and monomer, (a) a chromium-containing compound, (b) a hydrogenphosphite, and (c) an organomagnesium compound or (a) amolybdenum-containing compound, (b) a hydrogen phosphite, and (c) anorganoaluminum compound; and (3) adding the catalyst composition to themixture and thereby polymerizing the 1,3-butadiene monomer intosyndiotactic 1,2-polybutadiene within the rubber cement.
 2. The processof claim 1, where said step of providing the mixture of a rubber cementand 1,3-butadiene monomer comprises the step of preparing a rubbercement by polymerizing 1,3-butadiene monomer in an organic solvent toform high cis-1,4-polybutadiene, and then the step of adding additional1,3-butadiene monomer to the rubber cement.
 3. The process of claim 2,where said step of preparing a rubber cement by polymerizing1,3-butadiene monomer occurs in the presence of a lanthanide-basedcatalyst system.
 4. The process of claim 1, where said step of providingthe mixture of a rubber cement and 1,3-butadiene monomer comprises thestep of dissolving preformed rubber in an organic solvent, and then thestep of adding 1,3-butadiene monomer.
 5. The process of claim 2, wherethe organic solvent is n-pentane, n-hexane, n-heptane, n-octane,n-nonane, n-decane, isopentane, isohexanes, isoheptanes, isooctanes,2,2-dimethylbutane, petroleum ether, kerosene, petroleum spirits,cyclopentane, cyclohexane, methylcyclopentane, methylcyclohexane,benzene, toluene, xylenes, ethylbenzene, diethylbenzene, mesitylene, ora mixture thereof.
 6. The process of claim 4, where the organic solventis n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane,isopentane, isohexanes, isoheptanes, isooctanes, 2,2-dimethylbutane,petroleum ether, kerosene, petroleum spirits, cyclopentane, cyclohexane,methylcyclopentane, methylcyclohexane, benzene, toluene, xylenes,ethylbenzene, diethylbenzene, mesitylene, or a mixture thereof.
 7. Theprocess of claim 1, where said step of combining (a) achromium-containing compound, (b) a hydrogen phosphite, and (c) anorganomagnesium compound or said step of combining (a) amolybdenum-containing compound, (b) a hydrogen phosphite, and (c) anorganoaluminum compound, occurs in the presence of at least one type ofconjugated diene monomer.
 8. The process of claim 1, where said step ofadding the catalyst composition includes adding from about 0.01 to about2 mmol of the chromium-containing compound or molybdenum-containingcompound per 100 g of 1,3-butadiene.
 9. The process of claim 7, wherethe chromium-based catalyst composition is formed by first combining thechromium-containing compound and the hydrogen phosphite in the presenceof the at least one type of conjugated diene monomer to form an initialcomposition, followed by combining the initial composition with theorganomagnesium compound and, optionally, additional conjugated dienemonomer.
 10. The process of claim 7, where the chromium-based catalystcomposition is formed by first combining the chromium-containingcompound and the organomagnesium compound in the presence of the atleast one type of conjugated diene monomer to form an initialcomposition, followed by combining the initial composition with thehydrogen phosphite and, optionally, additional conjugated diene monomer.11. The process of claim 7, where the chromium-based catalystcomposition is formed by first combining the hydrogen phosphite and theorganomagnesium compound in the presence of the at least one type ofconjugated diene monomer to form an initial composition, followed bycombining the initial composition with the chromium-containing compoundand, optionally, additional conjugated diene monomer.
 12. The process ofclaim 7, where the chromium-based catalyst composition is formed byfirst combining the chromium-containing compound and the organomagnesiumcompound outside the presence of the at least one type of conjugateddiene monomer to form an initial composition, followed by combining theinitial composition with the hydrogen phosphite in the presence of theat least one type of conjugated diene monomer.
 13. The process of claim7, where the chromium-based catalyst composition is formed by firstcombining the chromium-containing compound and the hydrogen phosphiteoutside the presence of the at least one type of conjugated dienemonomer to form an initial composition, followed by combining theinitial composition with the organomagnesium compound in the presence ofthe at least one type of conjugated diene monomer.
 14. The process ofclaim 7, where the chromium-based catalyst composition is formed byfirst combining the hydrogen phosphite and the organomagnesium compoundoutside the presence of the at least one type of conjugated dienemonomer to form an initial composition, followed by combining theinitial composition with the chromium-containing compound in thepresence of the at least one type of conjugated diene monomer.
 15. Theprocess of claim 7, where the molybdenum-based catalyst composition isformed by first combining the molybdenum-containing compound and thehydrogen phosphite in the presence of the at least one type ofconjugated diene monomer to form an initial composition, followed bycombining the initial composition with the organoaluminum compound and,optionally, additional conjugated diene monomer.
 16. The process ofclaim 7, where the molybdenum-based catalyst composition is formed byfirst combining the molybdenum-containing compound and theorganoaluminum compound in the presence of the at least one type ofconjugated diene monomer to form an initial composition, followed bycombining the initial composition with the hydrogen phosphite and,optionally, additional conjugated diene monomer.
 17. The process ofclaim 7, where the molybdenum-based catalyst composition is formed byfirst combining the hydrogen phosphite and the organoaluminum compoundin the presence of the at least one type of conjugated diene monomer toform an initial composition, followed by combining the initialcomposition with the molybdenum-containing compound and, optionally,additional conjugated diene monomer.
 18. The process of claim 7, wherethe molybdenum-based catalyst composition is formed by first combiningthe molybdenum-containing compound and the organoaluminum compoundoutside the presence of the at least one type of conjugated dienemonomer to form an initial composition, followed by combining theinitial composition with the hydrogen phosphite in the presence of theat least one type of conjugated diene monomer.
 19. The process of claim7, where the molybdenum-based catalyst composition is formed by firstcombining the molybdenum-containing compound and the hydrogen phosphiteoutside the presence of the at least one type of conjugated dienemonomer to form an initial composition, followed by combining theinitial composition with the organoaluminum compound in the presence ofthe at least one type of conjugated diene monomer.
 20. The process ofclaim 7, where the molybdenum-based catalyst composition is formed byfirst combining the hydrogen phosphite and the organoaluminum compoundoutside the presence of the at least one type of conjugated dienemonomer to form an initial composition, followed by combining theinitial composition with the molybdenum-containing compound in thepresence of the at least one type of conjugated diene monomer.
 21. Theprocess of claim 1, where said rubber cement comprises highcis-1,4-polybutadiene.
 22. A process for preparing blends ofsyndiotactic 1,2-polybutadiene and rubbery elastomers comprising thesteps of: (1) providing a mixture of high cis-1,4-polybutadiene rubbercement and 1,3-butadiene monomer; and (2) preparing a catalystcomposition, where the catalyst composition is prepared by combining,outside the presence of the mixture of rubber cement and monomer, (a) achromium-containing compound, (b) a hydrogen phosphite, and (c) anorganomagnesium compound or (a) a molybdenum-containing compound, (b) ahydrogen phosphite, and (c) an organoaluminum compound; and (3) addingthe catalyst composition to the mixture and thereby polymerizing the1,3-butadiene monomer into syndiotactic 1,2-polybutadiene within therubber cement.
 23. The process of claim 22, where said step of providingthe mixture of high cis-1,4-polybutadiene rubber cement and1,3-butadiene monomer comprises the step of preparing a rubber cement bypolymerizing 1,3-butadiene monomer in an organic solvent to form highcis-1,4-polybutadiene, and then the step of adding additional1,3-butadiene monomer to the rubber cement.
 24. The process of claim 23,where said step of preparing a rubber cement by polymerizing1,3-butadiene monomer occurs in the presence of a lanthanide-basedcatalyst system.
 25. The process of claim 22, where said step ofproviding the mixture of a rubber cement and 1,3-butadiene monomercomprises the step of dissolving preformed high cis-1,4-polybutadiene inan organic solvent, and then the step of adding 1,3-butadiene monomer.